In mammals, the skin and mucosae constitute complex protective barriers that guard against infection and injury.
Phagocytes are the white blood cells that protect the body by ingesting harmful foreign particles and help initiate an immune response.
Natural killer (NK) cells are cytotoxic lymphocytes critical for the innate immune system.
Inflammation is part of the biological response of vascular tissues to harmful stimuli.
Antimicrobial peptides are an evolutionarily-conserved component of the innate immune response found among all classes of life.
Fever is an elevation of body temperature above the regulatory set point, mediated through the release of prostaglandin E2.
Evidence shows that stress has a negative effect on the body's immune system.
The adaptive immune system is composed of highly-specialized systemic cells and processes that eliminate or prevent pathogenic growth.
The adaptive immune response is mediated by B and T cells and creates immunity memory.
T cells originate from hematopoietic stem cells in the bone marrow and undergo positive and negative selection in the thymus to mature.
A lymphocyte is a type of white blood cell in the vertebrate immune system.
Antigen presentation is a process by which immune cells capture antigens and then enable their recognition by T cells.
Cytokines are small cell-signaling protein molecules secreted by numerous cells.
Antigens are molecules that initiate the immune response and can be bound by antibodies.
Haptens are molecules that create an immune response when attached to proteins.
Antigen epitopes make it possible for the immune system to recognize pathogens.
B cells mature in the bone marrow, where they undergo VDJ recombination to produce unique receptors that do not react to self-antigens.
An antibody is a Y-shaped protein produced by B cells to identify and neutralize antigens in the body.
The complement system is the ability of antibodies and phagocytic cells to remove pathogens from an organism.
Immunological memory refers to the ability of B and T cells to produce long-lived memory cells that defend against specific pathogens.
The major histocompatibility complex (MHC) is a cell surface molecule that regulates interactions between white blood cells and other cells.
Antigens are selected to form clones of themselves, both memory and effector.
T helper cells assist the maturation of B cells and memory B cells while activating cytotoxic T cells and macrophages.
The humoral immune response is the aspect of immunity mediated by secreted antibodies.
Early in life, the immune system is not mature enough to fight off pathogens and must depend on antibodies from the mother.
As aging occurs, the immune system begins to lose its ability to ward off pathogens.
Immunodeficiency is a state where the immune system's ability to fight infectious disease is impaired or absent.
Autoimmune diseases are an inappropriate immune response against tissues in the body.
A hypersensitivity reaction refers to an overreactive immune system triggered by allergies and autoimmunity.
Metastasis is the spread of cancer throughout the body.
The spleen acts as a blood filter for the body and can rupture due to trauma.
Pathogens have evolved mechanisms to evade capture by phagocytes in the immune system.
An abscess is a collection of pus that results from an infectious process, while an ulcer is a break or opening in the mucous membrane.
Immunotherapy is treating a disease by either inducing, enhancing or suppressing the immune system.
Transplant or graft rejection occurs when a transplanted tissue is rejected by the recipient's immune system.
Organ transplantation has both revolutionized medicine and led to technically, legally, and morally complicated situations.
Monoclonal antibodies are monospecific antibodies that recognize one specific epitope on a pathogen.
Cancer immunology examines the interaction between cancer cells and the immune system.
The hygiene hypothesis refers to lack of exposure to pathogens early in life, thus resulting in susceptibility to allergens.
Mononucleosis is an infectious disease caused by the Epstein-Barr virus (EBV) and results in flu-like symptoms.
Lymphoma is cancer of the lymphocytes and and is treated with chemotherapy or radiotherapy.
Systemic lupus erythematosus (SLE) is an autoimmune disease that can occur in any organ or tissue in the body.
The lymphatic system consists of lymphatic vessels and associated lymphoid organs.
The lymphatic system plays a prominent role in immune function, fatty acid absorption, and removal of interstitial fluid from tissues.
The lymphatic structure is based on that of blood vessels.
The lymphatic system comprises a network of conduits called lymphatic vessels that carry lymph unidirectionally towards the heart.
Lymph circulates to the lymph node via afferent lymphatic vessels and drains into the lymph node in the subcapsular sinus.
Lymph capillaries are tiny, thin-walled vessels, closed at one end and located in the spaces between cells throughout the body.
The lymph trunks drain into the lymph ducts, which in turn return lymph to the blood by emptying into the respective subclavian veins.
Lymphoid tissue consists of many organs that play a role in the production and maturation of lymphocytes in the immune response.
Lymph nodes are small oval-shaped balls of lymphatic tissue distributed widely throughout the body and linked by lymphatic vessels.
The thymus is a specialized organ that "educates" T cells or T lymphocytes, which are part of the adaptive immune system.
The spleen, similar to a large lymph node, acts primarily as a blood filter in the mononuclear phagocyte system of the immune system.
The tonsils are one of the immune system's first lines of defense against ingested or inhaled foreign pathogens.
Lymphatic tissue development begins by the end of the fifth week of embryonic development.